This B-25D Mitchell, the Yankee Warrior, is a World War II medium bomber which regularly flies out of Yankee Air Museum. / Detroit Free Press

General Motors Willow Run history • Built by Henry Ford in 1941, the plant made B-24 bombers during World War II and was later sold to General Motors. It has been empty since GM closed it in December 2010. • The woman who inspired the WWII propaganda image of “Rosie the Riveter” worked at the plant, which produced a bomber every 55 minutes at its peak during the war. • The plant, which GM acquired in the 1950s, employed a remarkable 42,000 people at the height of the war and some 14,000 during its heyday as an automotive factory in the 1970s. • Only 300 workers were employed there when it closed after making more than 82 million transmissions. • Much of the facility is out of date. Parts of the floor are made of wooden blocks.

The trust that controls the historic former General Motors Willow Run plant in Ypsilanti Township is likely to demolish the 5-million-square-foot factory with the exception of a portion that might be sold to the next-door Yankee Air Museum, the Free Press confirmed.

The factory, built by Henry Ford in 1941 to make B-24 bombers during World War II and later sold to GM, has been empty since GM closed it in December 2010. The woman who inspired the WWII propaganda image of “Rosie the Riveter” worked at the plant, which was pumping out a bomber every 55 minutes at its peak during the war.

The Yankee Air Museum, currently at several Willow Run Airport buildings adjacent to the plant, has signed a tentative deal to acquire a 175,000-square-foot portion of the factory that was once used to make the Liberator bombers. If the deal is completed, the museum would move from its existing 47,000-square-foot hangar and other properties.

But the museum must raise $6 million by Aug. 1 to complete the transaction or the entire structure will be torn down.

The museum is launching a fund-raising campaign to purchase the property from the Revitalizing Automotive Communities Environmental Response (RACER) Trust, which controls the properties GM discarded during its Chapter 11 bankruptcy in 2009.

RACER redevelopment manager Bruce Rasher said the trust would use the cleared land for redevelopment.

“The trust was not satisfied with the response we were getting from the market,” he said. “The overwhelming consensus — and the advice given to the trust — was that in order to take advantage of the significant amenities there like the airport and rail and highway, as well as being located near U-M and the Canadian border, the trust really needed to offer the market a blank slate.”

When the plant closed, few experts believed the entire property would survive, but a 1-million-square-foot portion that GM renovated in the 2000s was the most marketable portion.

Rasher said it’s still possible that part of the site could be sold and separated from the rest of the aging structure, but he called it a “fairly low probability.”

RACER has marketed the 332-acre property as an opportunity for aerospace, defense, port logistics and manufacturing, but so far the only sale has been a 23,000-square-foot portion to an aircraft maintenance firm, which plans to add 25 jobs.

The Yankee Air Museum would make renovations to the property as part of its deal to acquire a part of the facility.

Dennis Norton, who was the first Yankee Air Museum president, said the museum has already raised about $1 million for the 19.3-acre acquisition, which would include 700 parking spaces. He said the museum had been talking with the RACER trust for two years about acquiring the portion of the property where the bombers were manufactured.

The Aug. 1 deadline for the deal was “mutually agreed-upon,” but the museum is not required to complete the transaction if it can’t raise the cash, officials said.

“We need help raising money by then to save the plant. That’s the story — help save the bomber plant,” Norton said. “The only way we’re going to pull this off is to get all hands on deck in Michigan.”

Norton said the Smithsonian Institution has indicated that it would help the museum secure the only Willow Run-made B-24 bomber left in the U.S., if it can pull off the deal. He said the bomber, which is owned by the U.S. Air Force, is currently located on a military base in Shreveport, La.

The 32-year-old museum, which burned down in 2004 and reopened in 2010, said the bigger space would house all of its collections and exhibits, including planes that are currently not on display.

Visitors to the Willow Run plant are reminded of its heritage as a key player as the “Arsenal of Democracy” during the war. At the plant’s southeast corner, B-24 bombers would roll off the assembly line, exit through massive bay doors, taxi to the airport’s runway and take off.

Those bay doors are still there.

“The darn things still work,” Norton said. “They’re heavy doors, but they were so well built and evenly balanced, a fascinating piece of engineering.”

The trust has received interest from many different parties in parts of the plant, which spans 1.25 miles long. But many of the interested parties haven’t been serious leads.

Rasher said the site offers excellent opportunities for development because of its location — not because of its physical property.

He rejected the suggestion that the trust would tear down the property to reduce its property tax bill, which currently totals about $550,000. The trust was established with a different mission than the usual bankruptcy estate, he said.

“The trust’s mission is to attract a buyer that will make new investment, create jobs and revitalize the community,” he said. “That is our No. 1 focus, that is our No. 2 focus, that is our No. 3 focus. We are not in the business of trying to avoid paying taxes or not motivated by anything other than being a partner with the community and the state and ensuring there is an economic revitalization there.”

The trust is also managing a $36-million environmental cleanup budget at the site — part of a federal settlement with the Old GM. That work will continue, even after any future transactions are completed.

Contact: Nathan Bomey at 313-223-4743 or nbomey@freepress.com. Follow him on Twitter @NathanBomey.